Implement read validator.

The wrapper for IFX_SeekableReadStream.
Which allow us to check data availability on read request
and request downloading of non available data on fly.

Change-Id: I27c66cd58f43f8432f73104cc3f4c980515a9b56
Reviewed-on: https://pdfium-review.googlesource.com/9050
Commit-Queue: Art Snake <art-snake@yandex-team.ru>
Reviewed-by: (OOO Jul 28 - Aug 8) dsinclair <dsinclair@chromium.org>

1 files changed, 94 insertions, 0 deletions

diff --git a/core/fpdfapi/parser/cpdf_read_validator.cpp b/core/fpdfapi/parser/cpdf_read_validator.cpp
new file mode 100644
index 0000000000..148ecfd424
--- /dev/null
+++ b/core/fpdfapi/parser/cpdf_read_validator.cpp
@@ -0,0 +1,94 @@
+// Copyright 2017 PDFium Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+#include "core/fpdfapi/parser/cpdf_read_validator.h"
+
+#include <algorithm>
+
+#include "third_party/base/logging.h"
+
+namespace {
+
+constexpr FX_FILESIZE kAlignBlockValue = 512;
+
+FX_FILESIZE AlignDown(FX_FILESIZE offset) {
+  return offset > 0 ? (offset - offset % kAlignBlockValue) : 0;
+}
+
+FX_FILESIZE AlignUp(FX_FILESIZE offset) {
+  FX_SAFE_FILESIZE safe_result = AlignDown(offset);
+  safe_result += kAlignBlockValue;
+  if (safe_result.IsValid())
+    return safe_result.ValueOrDie();
+  return offset;
+}
+
+}  // namespace
+
+CPDF_ReadValidator::CPDF_ReadValidator(
+    const CFX_RetainPtr<IFX_SeekableReadStream>& file_read,
+    CPDF_DataAvail::FileAvail* file_avail)
+    : file_read_(file_read),
+      file_avail_(file_avail),
+      read_error_(false),
+      has_unavailable_data_(false) {
+  ASSERT(file_read_);
+}
+
+CPDF_ReadValidator::~CPDF_ReadValidator() {}
+
+void CPDF_ReadValidator::ResetErrors() {
+  read_error_ = false;
+  has_unavailable_data_ = false;
+}
+
+bool CPDF_ReadValidator::ReadBlock(void* buffer,
+                                   FX_FILESIZE offset,
+                                   size_t size) {
+  // correct values checks:
+  if (!pdfium::base::IsValueInRangeForNumericType<uint32_t>(size))
+    return false;
+
+  FX_SAFE_FILESIZE end_offset = offset;
+  end_offset += size;
+  if (!end_offset.IsValid() || end_offset.ValueOrDie() > GetSize())
+    return false;
+
+  if (!file_avail_ ||
+      file_avail_->IsDataAvail(offset, static_cast<uint32_t>(size))) {
+    if (file_read_->ReadBlock(buffer, offset, size))
+      return true;
+    read_error_ = true;
+  }
+  has_unavailable_data_ = true;
+  ScheduleDownload(offset, size);
+  return false;
+}
+
+FX_FILESIZE CPDF_ReadValidator::GetSize() {
+  return file_read_->GetSize();
+}
+
+void CPDF_ReadValidator::ScheduleDownload(FX_FILESIZE offset, size_t size) {
+  if (!hints_ || size == 0)
+    return;
+
+  const FX_FILESIZE start_segment_offset = AlignDown(offset);
+  FX_SAFE_FILESIZE end_segment_offset = offset;
+  end_segment_offset += size;
+  if (!end_segment_offset.IsValid()) {
+    NOTREACHED();
+    return;
+  }
+  end_segment_offset =
+      std::min(GetSize(), AlignUp(end_segment_offset.ValueOrDie()));
+
+  FX_SAFE_UINT32 segment_size = end_segment_offset;
+  segment_size -= start_segment_offset;
+  if (!segment_size.IsValid()) {
+    NOTREACHED();
+    return;
+  }
+  hints_->AddSegment(start_segment_offset, segment_size.ValueOrDie());
+}